Add "Windowing Systems by Example"

Closes #1005

Co-Authored-By: Sujal Singh <email.sujalsingh@gmail.com>

README.md

@@ -469,6 +469,7 @@ _For more general information, see OSDev.org_
 * [**Python**: _Learn ML Algorithms by coding: Decision Trees_](https://lethalbrains.com/learn-ml-algorithms-by-coding-decision-trees-439ac503c9a4)
 * [**Python**: _JSON Decoding Algorithm_](https://github.com/cheery/json-algorithm)
 * [**Python**: _Build your own Git plugin with python_](https://joshburns-xyz.vercel.app/posts/build-your-own-git-plugin)
+* [**Python**: _Windowing Systems by Example_](https://jmarlin.github.io/wsbe/)
 * [**Ruby**: _A Pedometer in the Real World_](http://aosabook.org/en/500L/a-pedometer-in-the-real-world.html)
 * [**Ruby**: _Creating a Linux Desktop application with Ruby_](https://iridakos.com/tutorials/2018/01/25/creating-a-gtk-todo-application-with-ruby)
 * [**Rust**: _Building a DNS server in Rust_](https://github.com/EmilHernvall/dnsguide/blob/master/README.md)